1. Field of the Invention
The disclosed invention and claims relate to the alcohol, polyol process for synthesizing metallic nanoparticles using a low temperature process.
2. Description of the Background Art
It is well known that glycols, glycerols, polyols, and glycolpolyesters at elevated temperatures reduce metal salts to nanoparticle sized metallic powders. The methods have been described in U.S. Pat. No. 5,759,230 ('230) and U.S. Pat. No. 4,539,041 ('041). The synthesis has also been described in NanoStructured Materials, 1995, 5(6), 607–612 and Appl. Phys. Lettr. 1997, 70(17), both publications and patents cited in this paragraph are incorporated herein by reference in their entirety. As well as synthesizing the metal and metal alloy particles, the polyol or alcohol synthesis can also be used to deposit nanocrystalline metals on various substrates including electronic substrates which are susceptible to hydrolytic degradation. The temperatures reported in the above cited documents range from 85–350° C., and reaction times from a few minutes to several hours are reported.
The above incorporated references suggest that high temperatures are preferred to speed metal precursor reduction reaction in alcoholic and polyol solvents. Also, high temperature reactions are thought to produce more uniform particle size in the metallic products. To increase reaction temperatures glycerin bp290° C., is used as a solvent either alone or in a solvent mixture. Also trioctylphosphine oxide and diphenyl ether may be used as solvents, either alone or in solvent mixtures.